MDEV-17349 Assertion `!table || (!table->read_set || bitmap_is_set(table->read_set, field_index))' failed on concurrent SELECT and DELETE after RENAME from table with index on virtual column

Race condition. field->flags were copied from s->field->flags during
field->clone(), early in open_table_from_share(). But s->field->flags
were getting their PART_INDIRECT_KEY_FLAG bit much later in
TABLE::mark_columns_used_by_virtual_fields() and only once per share.

If two threads were executing the code between field->clone()
and mark_columns_used_by_virtual_fields() at the same time, only
one would get PART_INDIRECT_KEY_FLAG bits in field[].